The invention set forth in this specification pertains to new and improved trailer suspension systems. More specifically, it relates to trailer suspension systems which tend to automatically steer a trailer in response to forces exerted as the trailer is turned in response to the vehicle towing it being turned or in response to cross-winds tending to move the trailer.
The term "trailer" as used in this specification is intended to designate any of a variety of different wheeled structures which are constructed so that they are adapted to be towed along a road or highway behind a vehicle such as a car, a van or the like. Such trailers are normally constructed so as to include a frame or chassis supporting a body constructed in accordance with the intended use of the trailer. On occasion the body of the trailer may be constructed so as to in effect serve as the frame or chassis of the trailer. Because of this, it is considered proper to refer to both the body of the trailer and the frame or chassis of the trailer more or less synonymously. Such a frame or chassis normally includes a so-called tongue extending from the front end of the trailer and supporting a coupler mechanism adapted to be secured to hitch on the towing vehicle in such a manner as to transmit forces corresponding to the movement of the towing vehicle to the trailer. Such trailers are normally constructed so as to utilize a suspension system supporting one or more wheels at each side of the trailer. Such wheels are normally located near the centers of the sides of the trailer. These wheels may be connected by axles extending between the sides of the trailer or they may be mounted upon the frame or chassis through the use of arms or similar members. In either case it is conventional to utilize springs or other resilient members in connection with the mounting of the wheels so as to accommodate vertical movement of the wheels in response to road surface irregularities and the like.
It is commonly recognized that a number of different factors are important in constructing a trailer so as to minimize the affects of the trailer on the operation of the towing vehicle and so as to provide a trailer structure which will "track" or go in a line following the path of the towing vehicle. It is not considered that an understanding of the present invention requires a detailed discussion of all of such factors. In general the greater the weight applied to the towing vehicle through the trailer hitch and tongue as a result of the construction or load of the trailer, the greater the effect of the trailer on the operation of the towing vehicle.
In the past it has been commonplace to attempt to improve the towing characteristics or towing ability of trailers by utilizing various different types of sway control devices and load equalizing devices not forming a part of a suspension system of a trailer. While the use of such auxiliary devices or mechanisms is in many respects satisfactory such use is nevertheless considered undesirable. A prime reason for this relates to economics; such devices cost money.
As a result of this, it is considered that there is a need to improve the construction of trailers so as to substantially eliminate the need for using sway control devices and weight distribution or equalizing devices. It is considered that this need is particularly important in connection with trailers which are intended to be towed behind comparatively small, comparatively lightweight towing vehicles such as, for example, comparatively small cars employing front wheel drive. In general, the lighter the weight of a towing vehicle the greater the affect of trailer tongue weight on the performance of the vehicle.
This letter is considered to be important with respect to the desirability of the present invention. It is considered that it is commonly recognized that reasonably satisfactory towing characteristics are related to a trailer being constructed or loaded so as to apply what may be referred to as a "moderate" weight to the towing vehicle through the trailer hitch and tongue. Such weights as have been used in the past have frequently been sufficiently great so as to significantly effect the performance and operation of comparatively small cars such as are increasingly being utilized.
As a result of this in order to provide trailers which can be satisfactorily towed behind such small vehicles trailers are increasingly being constructed which are comparatively light in weight and which are "balanced" relative to their wheels so that comparatively low tongue weights are applied to the towing vehicle through the trailer hitch. However, in the past it has been considered that the construction or loading of a trailer so as to minimize the tongue weight applied to a towing vehicle is considered somewhat disadvantageous as tending to detrimentally affect the towing characteristics or towability of the trailer.
As a consequence of this it is considered that there is a definite need for new and improved trailers which have satisfactory towing or towability characteristics even though such trailers are constructed so as to apply comparatively low tongue weights to a vehicle. Further, it is considered that there is a need for accomplishing such improvement without significantly increasing the cost or complexity of constructing such trailers.